I've done one but you have to take any progress 8 calculations with a huge grain of salt at this point in time.
It's based off David Potts example, linked above, but I've added an aspect for holding the expected attainment 8 for the student (pre calculated in excel and imported) You can then work out invidivual progress 8 and then use summary rows to get the overall.
If you set it up correctly you can then play with in Discover - this was the real eye opener for our SLT!
While the calculations are complex, I can't understand why they would be so complex that you couldn't do them in a marksheet.
Phil Neal, can you extend your answer at all?